Minor deflection yoke



Oct. 4, 1966 R.J.M1LLER MINOR DEFLECTION YOKE 5 Sheets-Sheet l Filed Dec. 4, 1965 ROBERT J. MILLER Oct. 4, 1966 Filed Dec. 4, 1965 ovERLAP LINE `e@LEADS R. J. MILLER MINOR DEFLECTION YOKE FIG. 2

5 Sheets-Sheet 2 OVERLAP LINE /7LEADS FIG?) INVENTOR. ROBERT J. MILLER HT .BNASI'S 3 Sheets-Sheet 5 Filed Dec. 4, 1965 N.. mzm m w25; m v/v vgl INVENTOR ROBERT J. MILLER United States Patent Otiice 3,277,411 Patented Oct. 4, 1966 3,277,411 MINOR DEFLECTION YOKE Robert J. Miller, San Bruno, Calif., assignor, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Filed Dec. 4, 1963, Ser. No. 328,145 1 Claim. (Cl. 335-212) This invention relates to a minor deflection yoke, and more particularly to an electromagnetic minor deilection yoke.

A minor deflection yoke generates two magnetic fields, in cartesian coordinates, to deflect an electron beam passing through the center of the neck of a cathode ray tube, referred to as the CRT, with which it is used. The deflection thus achieved is used for character writing or for the writing of symbols at a position on the cathode ray tubes phosphor screen dictated by the major deflection yoke and its associated drive circuits. Additionally such minor deflection yokes are used to modulate the electron beam of a CRT -used in a land mass simulator which utilizes a type of indicator requiring a radial sweep generated by .the major deflection yoke. By applying the proper modulating signals to the minor deflection yoke, it is possible to spread the radial sweep into an isoceles triangle, thereby simulating the beamwidth of a radar antenna. Such simulation can be achieved by applying appropriate ramp voltages, which are sinusoidally modulated, to such minor deflection yoke.

Previously minor deflection was accomplished by using a deflection yoke constructed so as to extend between the focus coil of the CRT and the end of the cathode ray tube gun structure nearest to the face of the cathode ray tube. Another way to achieve minor deflection is by designing a cathode ray tube, with electrostatic deflection plates, which `are driven by high-level vacuum tube amplifiers, external to such a CRT. When electromagnetic minor deflection yokes were constructed previously, its coils were wound in quadrature, without any consideration as to the environment in which the yoke was to be used. The proximity of other yokes, hardware, and the gun structure of the CRT generally upset the magnetic quadrature relationship of the pairs of coils comprising the minor deilection yoke. The result was a skewing of the cartesian coordinates of the two magnetic fields generated by the yoke, and cross-coupling between the two pairs of coils of the yoke when the signal applied to one coil interfered with the signal applied to the other coil of the yoke t-o drive l' it. The result was a distortion of the symbol, character,

or pattern being displayed on the phosphor of the C'RT.

One of the objects, therefore, of this invention, is to provide a minor deflection yoke which is capable of being adjusted to an exact quadrature relationship to compensate for .the distorting effects of adjacent electrical elements and hardware.

Additionally, when such minor deflection was accomplished, the electron beam, through six inches or less of the electron beams path of travel, was only affected, due to the particular positioning o-f the minor deflection yoke, as described previously, thereby yielding a lower deflection sensitivity than a yoke which is so located as to be capable of influencing the electron beam for the full length of the neck of the CRT past its cathode assembly. Such low deflection sensitivity of such types of yokes requires driving voltages of amplitudes available only from vacuum tube circuits, high-level vacuum tube amplifiers external to the CRT. Of course, the use of such vacuum tube circuits, which utilize high voltages, results in undesirable radio frequency interference necessitating shielding. Additionally, transistorized circuitry is not capable of supplying such high voltage amplitudes which are required for such construction.

Another object, therefore, of this invention, is to provide a minor deflection yoke having an improved deflection sensitivity.

A further object of the invention is to provide a minor deflection yoke which is capable of being driven by transistorized circuitry.

A still further object of this invention is to provide a minor deflection yoke, which avoids, to a substantial extent, the radio frequency interference shielding problems associated with other forms of minor deflection yokes.

`Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with, the accompanying drawings wherein:

FIG. la is a plan view of a final assembly of a portion of the minor deflection yoke, embodying the invention, and its relationship with other components in a cathode ray tube display device without the coil formers shown;

FIG. lb is an enlarged detail of FIG. lai showing the addition of coil former elements;

FIG. 2 is an elevational View of one coil of the pair of inner coils and its associated coil form, embodying the invention;

FIG. 3 is an elevational View of one coil of the pair of outer coils and its associated coil form, embodying the invention;

FIG. 4 is an elevational View of one pair of coils and its associated coil form, of another embodiment of the invention; and

FIG. 5 is a schematic diagram of one embodiment of the minor deflection yoke.

Similar numerals refer to similar parts throughout the several views.

Referring to FIG. l, the minor deflection yoke includes a lpair of outer coils, only one of which is shown, outer coil 2, a pair of inner coils, only one of which is shown, inner coil 4. The outer coil 2 is shown located on the neck 6 of the CRT S near the base 10 thereof, which is close to the cathode assembly, and extending to the very end of the neck `6. This outer coil 2, and all the others, are physically located below the focus coil 12, which is further up on the neck 6 and also below the major dellection yoke 14, which is very close to the screen end 16 of the neck 6 of the CRT 8. The inner coil 4 is similarly positioned except that each inner coilv is physically located dia-metrically opposite each outer coil. Additionally, there is provided several thumb screws, 1'8 and 20 which are used to adjust the quadrature relationship of the coils of the minor deflection yoke. The inner and outer coils are positioned so that they are capable of being rotated on the neck 6 of the tube 8, and with respect to one another, so as to provide an exact quadrature magnetic field, thereby compensating for the distorting effects of adjacent structure. Referring to FIGS. 2 and 3, this minor deflection yoke may be composed of two identical pairs of coils. Each individual coil, 22 and 24, of each pair is formed on a cylindrical coil form 26 and 28 respectively, which are made to fit one inside the other, so as to be free to rotate about the neck 6 of the CRT 8, and with respect to one another. In the nal assembly, the long dimension o-f each pair of coils is diametrically opposite to each other as they exist on the neck 6 of the CRT 8, so as to provide an accurate magnetic quadrature field. Still referring to FIGS. 2 and 3, there is illustrated one embodiment of this minor deflection yoke which could be used with a CRT, having an 1%6 outside diameter neck. It should be observed at this point that each of the dimensions illustrated is a nominal dimension. Each individual coil, of each pair of coils, are constructed from three turns of 40/ 44 litz wire coated with nylon Formvar or the equivalent (no enamel).

Each individual coil is attached to a non-metallic, flexible sheet of coil supporting material, and the Wires when laid thereon, should be positioned as close as possible, without lump-forming cross-overs. Each coil has a lead length of approximately 24 inches. Each of the coil formers longitudinal dimensions are different so as to allow adjustment, the longest being the coil former which is nearest the surface of the CRTs neck. The outer coil assembly illustrated in FIG. 3 is substantially the same as that shown in FIG. 2 except that the length of the coil former sheet 28 is one inch less than that of the inner coil former sheet 26. FIG. 4 shows another embodiment, wherein the two individual coils 2 and 30 which make up one pair of the coils for the minor deflection yoke are actually secured to one coil former 32 thereby requiring only two cylinders which are adjustable on 4the neck 6 of the CRT 8, and with respect to one another. Each of such pair of coil windings can be formed on an individual cylinder which is coated with plastic so as to embed the windings therein. The second pair of coils would be formed in the same manner, but on a cylinder of a different diameter so as to permit one pair of coil assemblies to slide and rotate within the other. \In this manner, a seam or joint is eliminated, whe-reas the sheets illustrated in FIGS. 2 and 3 would overlap on itself, which could catch on the exterior yoke during alignment procedures. BIG. 1b illustrates this embodiment, wherein the two pairs of coils are secured on two cylinders, outer cylinder 32 formed by rolling coil former 32 into a cylinder and inne-r cylinder 34 formed from a similar coil former (not shown). The electrical connections for the two pair of coils are illustrated in FIG. 5. lEach pair of coils is connected in parallel aiding and their physical relationship is such as to provide a quadrature magnetic lield. After the two pairs of coils have been installed on the neck 6 of the CRT 8, the two concentric cylinders 32 and 34 on which the two pairs of coils are mounted, are rotated with respect to each other until the cross-coupling is at a minimum. One method of doing this is to drive one pair of winding with a two or three megacycle signal source and monitoring the output of the other pairs o-f coils on an oscilloscope and adjust the quadrature relationship of the two pairs of coils for null at the output. This setting, or nulled position of the two pairs of coils, establishes a quadrature relationship that takes into account the environment in which a yoke must operate. This is not true, however, of other forms of deliection yokes. Additionally, the construction of this minor deilection yoke makes use of the full length, or substantially the full length of the cathode ray tubes neck, resulting in greater deflection sensitivity t-han is available with other forms of minor dellection yokes, thereby allowing the usel of transistor circuitry, and eliminating to a great extent, shielding problems.

Once the quadrature relationship of the two pairs of coils of the minor deflection yoke are properly set, as 5 described supra, both pairs of coils of the yoke are rotated together, about the neck `6 of the CRT so as to position the symbol, character or pattern right-side up on the phosphor screen 16. Positioning electrical signals to the minor deflection yoke can be varied from direct current to live megacycles, and the drive source can be transistorized or vacuum tubes may be utilized, the latter being much less eltective. A maximum of about 2() degrees deflection angle can be achieved.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. lt is therefore to be understood that within the scope of the appended claim the invention may be practiced otherwise than as speciiically described.

What is claimed is:

A deflection system for a cathode ray tube having a neck portion, a cathode, a focusing means, and a screen comprising in combination,

a. a minor dellection yoke b. a major deection yoke c. said minor deflection yoke including a first electromagnetic deflection means, a second electromagnetic deflection means and adjustable securing means connecting each of said deflection means to the neck portion of said tube, each of said electromagnetic means being physically located around the neck portion of the cathode ray tube and independently adjustably secured to said neck by said adjustable securing means for movement with respect to said .tube neck and to one another, so as to accurately provide by independent adjustment of said first and second electromagnetic deflection means, a quadrature magnetic deflection eld, and each deflection means being dimensioned to extend longitudinally over substantially the entire length of said cathode tube neck,

d. said major deflection yoke being mounted concentric about said minor deflection yoke and adjacent said screen.

References Cited by the Examiner UNITED STATES PATENTS 2,845,562 7/1958` Bendell et al 317-200 X 3,111,609 ll/l963 Webb 3l7-200 BERNARD A. GtILHEANY, Primary Examiner.

G. HARRIS, JR., Assistant Examiner. 

